Apparatus for the electrical transmission of sound from gramophone records



.Itfne 10, 1930. L PEARSON 1,762,834

APPARATUS FOR THE ELECTRICAL TRANSMISSION OF SOUND FROM GRAMOPHONERECORDS Filed Nov-. 1928 M IL . his is provided Patented June 10, 1930 ALAURENCE HERBERT PEARSQ N, OF NOTTINGHAM, ENGLAND APPARATUS FOR rHRnLEc'rRIcAL 'rRANsM'IssIoN or soUNn FROM REcoRns Application filedNovember 3, 1928, Serial No.

This invention comprises improvements in or relating to apparatus forthe electrical transmission of sound from gramophone records, the classof apparatus to which the invention has more particular reference beingthat .wherein an electrical device known as a pick up or collector is.attached to the gramophone tone arm and coacts with the record so as toinduce in said pick up varying electrical impulses which are suitablyamplified and conveyed to a loud speaker or equivalent reproducinginstrument.

Apparatus of this kind is able for use in cinemas and other places ofamusement'for supplying orchestral and other music. 1

According-to the present invention apparaembodying a plurality ofgramophone record turn-tables, an electrical pick up for coacting witheach record, sound amplifying means, means for transmitting sound fromthe records of said turn-tables in succession and means whereby afterthe last record of a series has been completed re-transmission from therecords in succession may be automatically recommenced or automaticallystopped.

It is to be understood that in connection with apparatus functioning inaccordance with the present invention means for superimposing one recordupon another may also be incorporated but any known or desirable meansfor superimposing may be employed and such means per se constitute nopart of the present invention. I

A feature of the invention consists in the provision of relays and meanswhereby on manipulation of a unit control the relays are set for therecords to be brought into opera: tion in succession. A further featureconsists in the provision of a two-way electrical switch associated withthe series and so.

the last or final record of arranged that in one position the switchfunctions to cause the records to be brought into operation insuccession and in the same sequence as before whilst in the otherposition the switch functions to terminate transmission from therecords.

For thepurpose of more fully describing formers T T particularly suit-316,919, and in Great Britain October 5, 1928.

the nature of .this invention reference will now be made totheaccompanying drawing wherein is shown a circuit diagram illustrating aconvenient method of carrying out the invention.

In the particular embodiment illustrated, three gramophone turntablesare indicated at G G G each of the tone arms TA TA TA associatedtherewith having detachably attached thereto an electrical pick up P PP, included in the primary circuits of trans- T respectively. The recordturntables are driven by independent electric motors M M M Associatedwith eachtone arm is a sliding contact TC TC TC which are adapted to betraversed between parallel guide barsB into and out of engagement withpairs of .spaced contacts C C C, said last named contactsbeing carriedby an insulator which is adjustable length-Wise of thebarsB. Each of thesaid contacts C 0 ,0 is so adjusted that the respective sliding contactsTC, TC

TC, in traversing the bars B as the tone arms traverse the record bridgesuch contacts when transmission from the records is completed. Theelectrical current in ut terminals are indicated at I, a line switclibeing preferably included at IL, and MOS is a master switch whichgoverns the current supply to the apparatus and is moved to the on oroff position by selectively energizing and de-enerhe two relays CR CRgizingt In operation, the master switch MOS is first closed (as shown inthe diagram) by energizing relay CR This may be accom plished b .drawingri ht bac so as to cause the sliding contact T 1 to engage and bridge apair of fixed con-- rags SC, thus closing the circuit of relaySimultaneously with the closing of switch MCS consequent upon contact T0bridging the contacts SC, relays RY and RY are energized to attracttheir respective armature AR AR Associated with-the relays KY RY arerespectively relays KY KY The arrangement of these relays and armaturesAR AR is such that the armatures, after being operat d by one of therelays, will reemornonn the first tone armTA main in such operativeposition even after the relay in question ceases-to be energized. Forthis reason the armatures AR AR are preferably balanced armatures.

The energization of the relays RY RY and the operation of the armaturesAB AR thereby, as previously described, effects closure of contacts MSTS M8 TS and consequently by the simple operaton of the contact TC inthe manner described the Whole apparatus'is electrically (as distinctfrom mechanically) set for starting.

Assuming that it is desired to transmit the sound from the three recordsin succession the records will preferably be first .placed on eachturntable and after the apparatus has been electrically set as beforedescribed each pick up will be brought into-contact with its respectiverecord. Then upon completion of the circuit of the motor M by closure ofswitch MSG transmission of soundfrom the first gramophone record iscommenced, the pick up P -being located in the primary circuit of thetransformer T as previously explained and the secondary of suchtransformer being across potentiometer V to thermionic valve VA As thetone arm TA traverses the record of the first gramophone the contact TCmoves alon the guides B and when the end of the recor is reached suchcontact bridges fixed contacts C and thereby energizes relay KY Theeffect of energizing such relay is to attract the armature AR and opencontacts M3 and TS and bring the motor M to rest. At the same timecontacts MS are closed and thereby complete the circuit of motor Mdriving the second gramophone record and contacts TS are closed whichshort the secondary of transformer T and thereby prevent thetransmission of further sound from the firstirecord. By virtue ofshorting the secondary of transformer T the transmission of any slurringsounds is definitely avoided.

It will also be noticed that the armature AR opens the contacts T8 whichwhen closed short-circuit the secondary of transformer T included in thecircuit of the pick up P of the gramophone G and transmission of soundfrom the record of such gramophone is thereby enabled,'the said pick upbeing connected through transformer T and potentiometer V to valve VA itbeing understood that whilst the first gramo bone was in operationclosure ofcontacts T 2 and T5 prevented the transmission of sounds fromthe pick up P, P respectively and thereby avoid-- ed interruption suchas would be occasioned if the pick ups were disturbed during. thetransmission of sound from gramophone G Upon completion of transmissionof sound from the gramophone Gr contact TC slidin along the bridge Bcloses the contact C an thereby operates relay RY which attracts thearmature AR opens the contacts M8 record of gramophone TS? andtherebybrings the motor lVL to rest and opens the short circuit across thesecondary of transformer T closes contact MS and so completes thecircuit of motor M and at the same time closes contacts TO toshortcircuit the secondary of transformer T and thereby preventtransmission of further sound from the pick up P and the avoidance ofunders-irable noises due to slurring or other causes.

The pick up P bein in contact with the now transmits the sound from suchrecord through the medium or thermionic valve VA which-is connected to apotentiometer V included in the secondary circuit of transformer T theprimary of which is in series with the pick up P Upon completion of thetransmission of sound from the record ofgramophone G the contacts C arebridged. Associated in the circuit of such contacts is a two-Way switchSSE. In one position, when in contact with the contact S, relay CR isenergized upon the contacts C 1 being bridged by ing of course that thepick up of such gramophone has been previously -moved back to thestarting position, although not sufliciently far back "for contact T0 tobridge contacts SC, it being appreciated that when the switch SSR isincontact with contact R completion of the contacts C by the slidingcontact 'lC forms the same function as closure of contacts SC by slidingcontact TC The contact S is preferably marked Stop and the contact RRepeat and when it-is desired to repeat transmission the contact ismoved to the position R and during the time that sound is beingtransmitted from the third gramophone record the first and secondgramophones are adjusted to their starting position and if it isdesired-the records are changed during this time.

'In order to avoid the transmission of sound from the records before theturntables have obtained the desired speed of rotation governors may beassociated with each motor,

the arrangement being such that when the motor speed falls belew apre-determined minimum a short-circuit is effected and transmission ofsound thereby prevented. Conveniently the governor may function toshortcircuit the transformer secondary circuit. By these-means thetransmission of slurring sounds during the time that the motor isinitially-gaining speed is definitely avoided and under no circumstanceswill sound be transmitted unless the speed of the motor assumes posingeffects i each case the arrangement 1,762,834 I I I and maintains therequisite predetermined minimum. v

.The purpose of the potentiometer V V V is to control the volume outputfrom'each pick up and this provision enables difierent types of recordsto be handled satisfactorily.- Moreoverif sound from another independentrecord is being superimposed upon that produced by any one of therecords brought into I operation in sequence in the manner hereindescribed'the provision of the aforesaid potentiometer enables controlof the S'llPGIlIIlto be obtained.

Although in the drawings only three rec-" ords have been shown it is tobe understood that any number may be provided, and in as describedherein is such that whensound is beingtransmitted from one record theelectrical output circuit from the other records 'is shorted so thatmanipulation or movement of the pickups associated with the otherrecords will not 111- terfere with the transmission from the record thatis being played at any time, Again ineach case the arrangement willbefsuch that after transmission from a record has been n com leted theoutput circuit 'is immediate 1y 5 ort-circuited' so that no slurringnoises or other noises which ma arise subsequent to, transmission arepasse through the amplifier.

I claim 1; Apparatus turntable for coacting with eac sound amplifyingmeans,

loutput circuits of th tion of sound from gramophone records comprising"a plurality of turntables and driving motors therefor, an electric picku for each record, a pair of rela s associated with each turntable otherthan the lastof the series of turntables, balanced armatures adapted foroperation by said relays, I I n the motor circuits and pickups-associated with the several turntables, and a unit control switchassociated with the tone arm of the first turntable, said switchoperating the re-. lays to close the motor circuit ofsuch turntable andshort-circuit tpick ups of all the ther turntables and .amanuallyoperable switch controlling the opening and closing of the motorcircuit ofvthe first said relays controlling turntable LAURENCE HERBERTPEARSON.

for the electrical reproduc- I tion of sound from gramophon'e recordscomf I plurality of turntables and drivin risin a p g pick up for eacmotors therefor, an electric turntable for coacting witheach record,sound last of the series of turntables,

the several turntables, a

tion of sound from gramophone recor prising a plurality of turntablesand driving am 1i in means, a air 3i relays associated wit gch turntableotheflthan the last of the series ,ofturntables, balanced armaturesadapted for operation by said relays, said relays controlling the motorcircuits and output circuits of the pick ups associated with air ofcontacts associated with each turntab e, a member moving in unison withthe table and said member closing the-respective contacts to operate therespective relays.

'2. Apparatus for the electrical reproduc com- an electric pick u foreach turntable for coacting with eac f record, sound amplifying means, apair of relays as-' sociated with each turntable other than the balancedarmamotors therefor,

tures adapted for operation by said relays,

saidrelayscontrolling the motor circuits and output circuits of the pickups associated with the several turntables, a unit switch associatedwith the first turntable, said switch operating the relays associatedwith each 'tive balanced turntable, said relays actuating their respecarmatures to close the motor c1rcu1t of the first turntable andshort-circuit tone arm of each turne output from the;

Ht) I Ilfli)

